This invention relates to a waterproof plug for a waterproof connector.
A waterproof connector includes a housing in which a terminal connecting a cable is received. The housing includes a receiving chamber for receiving the terminal, an opening through which the interior and exterior of the housing communicate with each other, and a communication portion through which the opening and the receiving chamber communicate with each other. The cable can be connected to the terminal through this opening. A rubber plug, having a through hole (in which the cable can be press-fitted) is used as a waterproof seal, and is fitted in the housing. An inner surface of the through hole is corrugated in a direction of the axis of the through hole, and has larger-diameter portions and smaller-diameter portions. The smaller-diameter portions are designed to have a diameter smaller than the outer diameter of the cable, and the smaller-diameter portions are adapted to be held in intimate contact with the cable because of their own elasticity, thereby preventing water from intruding into the housing.
When the cable is not connected to the waterproof connector, a waterproof plug of a cylindrical shape, having the same diameter as that of the cable, is press-fitted in the through hole (through which the cable is to be passed) in the rubber plug to close this through hole. In order to prevent such a waterproof plug from being disengaged from the rubber plug, there has been proposed a construction in which a pair of retaining projections are formed at each of opposite ends of the waterproof plug, and project symmetrically respectively in opposite directions perpendicular to the axis of the waterproof plug, and these retaining projections restrict the axial movement of the waterproof plug (see, for example, JP-A-2001-357927, especially, pages 2 to 3, FIGS. 1 to 2). Crest surfaces of the retaining projections, formed at one end portion of this waterproof plug, are slanting and tapering toward a tip or distal end thereof, and this tapering end portion is inserted into the through hole, thereby attaching the waterproof plug to the rubber plug.
However, when the waterproof plug, described in JP-A-2001-357927, is inserted into the through hole in the rubber plug, there is a fear that the smaller-diameter portions (that is, lip portions) on the inner surface of the through hole are damaged by the retaining projections formed at the end portions of the waterproof plug. When the lip portions are thus damaged, the ability of the rubber plug to be held in intimate contact with the cable or the waterproof plug is deteriorated, which leads to a possibility that the waterproof performance of the rubber plug is lowered.